On Mon, Jul 29, 2013 at 08:01:23AM -0600, Chris Murphy wrote:
On Jul 29, 2013, at 6:30 AM, "Daniel P. Berrange" <berrange(a)redhat.com>
wrote:
> Yep, we need to be able to report free space on filesystems, so that
> apps provisioning virtual machines can get an idea of how much storage
> they can provide to VMs without risk of over comitting.
>
> I agree that we really want the kernel, or at least a reusable shared
> library, to provide some kind of interface to determine this, rather
> than requiring every userspace app which cares to re-invent the wheel.
What does it mean for an app to use stat to get free space, and then
proceeds to create too big a VM image in a directory that has a quota
set? I still think apps are asking an inappropriate/unqualified question
by asking for volume free space, instead of what's available to them for
a specified path.
From an API POV, libvirt doesn't need/care about the free space on
the
volume underlying the filesystem. We actually only care about the free
space in a given directory that we're using for disk images. It just
happens that we implement this using statvfs() currently. So when I
ask for an API above, don't take this to mean I want a statvfs() that
knows about sparse volumes. An API or syscall that provides free space
for individual directories is fine with me.
Daniel
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